Myocardial lead

ABSTRACT

The present invention is a lead for use in connection with a myocardial lead attachment system of the type having an anchor for engaging the heart and a tether extending from the anchor. The lead includes a lead body having a proximal end, a distal end and a lumen for accepting the tether. A tapered tip is separate from the lead and positioned adjacent the distal end of the lead. The tip has a longitudinal through-hole for accepting the tether.

REFERENCES

The present application claims the benefit of the following U.S. Provisional Applications: Application Ser. No. 60/514,037 filed Oct. 24, 2003, entitled “Absorbable Myocardial Lead Fixation System”, Application Ser. No. 60/514,665 filed Oct. 27, 2003, entitled “Lead Electrode Arrangement for Myocardial Leads”, Application Ser. No. 60/514,042 filed Oct. 24, 2003, entitled “Tapered Tip for Myocardial Lead”, Application Ser. No. 60/514,714 filed Oct. 27, 2003, entitled “Minimally-Invasive Fixation Systems for Over-the-Tether Myocardial Leads”, Application Ser. No. 60/514,039 filed Oct. 24, 2003, entitled “Distal or Proximal Fixation of Over-the-Suture Myocardial Leads”, Application Ser. No. 60/514,146 filed Oct. 24, 2003, entitled “Myocardial Lead with Fixation Mechanism”, Application Ser. No. 60/514,038 filed Oct. 24, 2003 entitled “Delivery Instrument for Myocardial Lead Placement” and Application Ser. No. 60/514,713 filed Oct. 27, 2003, entitled “Drug-Eluting Myocardial Leads”, all of which are incorporated herein by reference.

Reference is hereby made to the following commonly assigned U.S. patent application Ser. No. 10/821,421, filed Apr. 9, 2004, entitled “Cardiac Electrode Anchoring System” and the following commonly assigned U.S. patent applications filed on an even date herewith, all of which are incorporated herein by reference: application Ser. No. ______, entitled “Myocardial Lead Attachment System”, application Ser. No. ______, entitled “Distal or Proximal Fixation of Over-the-Tether Myocardial Leads”, application Ser. No. ______, entitled “Myocardial Lead with Fixation Mechanism” and application Ser. No. ______, entitled “Absorbable Myocardial Lead Fixation System.”

FIELD OF THE INVENTION

This invention relates generally to implantable lead assemblies for stimulating and/or sensing electrical signals in muscle tissue. More particularly, it relates to myocardially-implanted leads for cardiac stimulation and systems for anchor the leads.

BACKGROUND OF THE INVENTION

Cardiac rhythm management systems are used to treat heart arrhythmias. Pacemaker systems are commonly implanted in patients to treat bradycardia (i.e., abnormally slow heart rate). A pacemaker system includes an implantable pulse generator and leads, which form the electrical connection between the implantable pulse generator and the heart. An implantable cardioverter defibrillator (“ICD”) is used to treat tachycardia (i.e., abnormally rapid heart rate). An ICD also includes a pulse generator and leads that deliver electrical energy to the heart.

The leads coupling the pulse generator to the cardiac muscle are commonly used for delivering an electrical pulse to the cardiac muscle, for sensing electrical signals produced in the cardiac muscle, or for both delivering and sensing. The leads are susceptible to categorization according to the type of connection they form with the heart. An endocardial lead includes at least one electrode at or near its distal tip adapted to contact the endocardium (i.e., the tissue lining the inside of the heart). An epicardial lead includes at least one electrode at or near its distal tip adapted to contact the epicardium (i.e., the tissue lining the outside of the heart). Finally, a myocardial lead includes at least one electrode at or near its distal tip inserted into the heart muscle or myocardium (i.e., the muscle sandwiched between the endocardium and epicardium). Some leads have multiple spaced apart distal electrodes at differing polarities and are known as bipolar type leads. The spacing between the electrodes can affect lead performance and the quality of the electrical signal transmitted or sensed through the heart tissue.

The lead typically consists of a flexible conductor surrounded by an insulating tube or sheath that extends from the electrode at the distal end to a connector pin at the proximal end. Endocardial leads are typically delivered transvenously to the right atrium or ventricle and commonly employ tines at a distal end for engaging the trabeculae.

The treatment of congestive heart failure (“CHF”), however, often requires left ventricular stimulation either alone or in conjunction with right ventricular stimulation. For example, cardiac resynchronization therapy (“CRT”) (also commonly referred to as biventricular pacing) is an emerging treatment for heart failure, which requires stimulation of both the right and the left ventricle to increase cardiac output. Left ventricular stimulation requires placement of a lead in or on the left ventricle near the apex of the heart. One technique for left ventricular lead placement is to expose the heart by way of a thoracotomy. The lead is then positioned so that the electrodes contact the epicardium or are embedded in the myocardium. Another method is to advance an epicardial lead endovenously into the coronary sinus and then advance the lead through a lateral vein of the left ventricle. The electrodes are positioned to contact the epicardial surface of the left ventricle.

Unfortunately, insertion through the myocardium can be somewhat traumatic to the muscle tissue. Accordingly, there is a need for a lead that can be implanted with minimal long-term damage to the physiology of the heart.

SUMMARY OF THE INVENTION

According to one embodiment, the present invention is a lead for use in connection with a myocardial lead attachment system of the type having an anchor for engaging the heart and a tether extending from the anchor. The lead includes a lead body having a proximal end, a distal end and a lumen for accepting the tether. A tapered tip is separate from the lead body and is positioned adjacent the distal end of the lead body. The tip has a longitudinal through-hole for accepting the tether.

According to another embodiment, the present invention is a method of implanting a myocardial lead. An anchor mechanism coupled to a distal end of a tether is advanced through the myocardium to an implant site. An appropriate dilating tip having an internal through-hole is selected. The tip and lead are threaded onto the tether such that the tip is distal to the lead. The tip and lead are advanced over the tether to the implant site.

According to another embodiment, the present invention is a method of implanting a lead into a myocardium of a heart. A proximal end of an anchor mechanism and tether arrangement is attached to a needle. The needle is advanced through the heart at least until the proximal end of the tether 45 exits the heart. The needle is detached from the tether and the proximal end of the tether is tensioned to cause the anchor mechanism to engage the heart. A lead is advanced over the tether into the heart.

This summary is not intended to describe each embodiment or every implementation of the present invention. Advantages and a more complete understanding of the invention will become apparent upon review of the detailed description and claims in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view of a patient's heart showing a portion of the vasculature and a myocardial lead attachment and pacing system according to one embodiment of the present invention.

FIG. 2 is a side sectional view of a distal portion of the myocardial lead attachment system of FIG. 1 in accordance with one embodiment of the present invention.

FIG. 3 is a side sectional view of a distal portion of the myocardial lead attachment system of FIG. 1 in accordance with another embodiment of the present invention.

FIG. 4 is a side sectional view of a distal portion of the myocardial lead attachment system of FIG. 1 in accordance with yet another embodiment of the present invention.

FIG. 5 is a side sectional view of a distal portion of the myocardial lead attachment system of FIG. 1 in accordance with still another embodiment of the present invention.

FIG. 6A is a side sectional view of a distal portion of the myocardial lead attachment system of FIG. 1 in accordance with another embodiment of the present invention.

FIG. 6B is a side sectional view of the attachment system of FIG. 6A following removal of the tip.

FIG. 7 is a perspective view of a distal portion of the myocardial lead attachment system of FIG. 1 in accordance with yet another embodiment of the present invention.

While the invention is amenable to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and are described in detail below. The intention, however, is not to limit the invention to the particular embodiments described. On the contrary, the invention is intended to cover all modifications, equivalents, and alternatives falling within the scope of the invention as defined by the appended claims.

DETAILED DESCRIPTION

FIG. 1 shows a myocardial lead attachment and pacing system 10 deployed in a human heart 12 according to one embodiment of the present invention. The heart 12 includes a right atrium 14 and a right ventricle 16 separated from a left atrium 18 and a left ventricle 20 by a septum 22. During normal operation of the heart 12, deoxygenated blood is fed into the right atrium 14 through the superior vena cava 24 and the inferior vena cava 26. The deoxygenated blood flows from the right atrium 14 into the right ventricle 16. The deoxygenated blood is pumped from the right ventricle 16 into the lungs, where the blood is re-oxygenated. From the lungs the oxygenated blood flows into the left atrium 18, then into the left ventricle 20. The left ventricle 20 beats forcefully to pump the oxygenated blood throughout the body.

The outer walls of the heart 12 are lined with a tissue known as the epicardium 28. The inner walls of the heart are lined with a tissue known as the endocardium 30. The heart muscle, or myocardium 32, is sandwiched between the endocardium 30 and the epicardium 28. A tough outer pericardial sac 33 surrounds the heart 12.

The pacing system 10 includes a pulse generator 34 coupled to a myocardial lead 36. The pulse generator 34 is typically implanted in a pocket formed underneath the skin of the patient's chest or abdominal region. The lead 36 extends from the pulse generator 34 to the heart 12 and is implanted in the myocardium 32 near an apex 38 of the left ventricle 20. The lead 36 delivers electrical signals from the pulse generator 34 to at least one electrode located at or near a distal region of the lead 36 to accomplish pacing of the heart 12 (not visible in FIG. 1). Although shown in implanted near the apex 38, the lead 36 may be implanted anywhere in the heart 12 pacing therapy is needed. An anchor mechanism 44 is coupled to the lead 36 via a tether 45 to secure the lead 36 to the heart 12 and to facilitate delivery of the lead 36 into the heart 12.

The pacing lead assembly 36 and anchor mechanism 44 may be implanted in the heart 12 with a delivery instrument and according to methods described in the above-identified application “Myocardial Lead Attachment System”. Briefly, the delivery instrument and anchor mechanism 44 are advanced through the heart 12, forming a tract through the myocardium 32 (not visible in FIG. 1). The anchor mechanism 44 is deployed on a surface of the heart 12 so that the tether 45 extends longitudinally through the tract. Following implantation of the anchor mechanism 44, the tether 45 is threaded through the lead 36 and the lead 36 is advanced over the tether 45 into the myocardium 32. The tether 45 is then tensioned and attached to the lead 36 to secure the lead 36 in place within the myocardium 32. This structure results in a locally-stable myocardial implant.

Optionally, the anchor mechanism 44 may be implanted without the aid of a delivery instrument as is described above, but rather with a curved suture needle. The proximal end of the tether 45 is attached to the needle, either directly or to a short length of suture attached to the needle. The needle is used to pierce the epicardium 28, is pushed through the myocardium 32 and drawn back through the epicardium 28, pulling the tether 45 through the myocardium 32. The tether 45 is cut from the needle and tensioned to bring the anchor mechanism 44 in contact with the epicardium 28. The lead 36 is threaded onto the tether 45 and advanced over the tether 45 as previously described.

FIG. 2 is a sectional view of a distal portion of the myocardial lead attachment system 10 according to one embodiment of the present invention. The myocardial lead 36 includes two electrodes, a proximal anode 40 a and a distal cathode 40 b. An outer insulating sheath 46 is formed around the lead 36 and protects a pair of coiled conductive members 48 a and 48 b coupled to the anode 40 a and cathode 40 b, respectively. A second inner insulating sheath 50 forms an internal lumen 43 for receiving the tether 45. A marker band 52 is optionally formed on the outer insulating sheath 46.

The lead 36 includes a tapered tip 54 positioned distal to the distal region 42 of the lead 36. The tapered tip 54 tapers from a first diameter a at a proximal end 54 a to a second diameter b, smaller than the first diameter a, at a distal end 54 b. In one embodiment, as shown in FIG. 2, the tapered tip 54 is formed in the shape of a cone. In another embodiment, shown in FIG. 3, the tip 54 is more rounded and is formed in the shape of a bullet. A bore 56 extends through the tip 54 in communication with the lumen 43 for receiving the tether 45.

As the lead 36 is advanced over the tether 45 through the during insertion, the tapered tip 54 does not cut through the myocardial tissue 32, but rather dissects or dilates the tissue. The tapered tip 54 provides a streamlined leading edge to the lead 36, reducing trauma to the myocardium 32. According to one embodiment, the diameter a of the proximal end 54 a is greater than a diameter of the lead 36. Such a tip 54 gently dilates or expand the tract to facilitate advancement of the lead 36. According to other embodiments, the tip 54 has any shape having rounded edges and a streamlined shape chosen to reduce trauma to the myocardium 32 during insertion.

Prior to lead implantation, the tip 54 may be selected from a plurality of tips having differing shapes based on the physiology of the heart 12. Where the epicardium 28 and or pericardium 33 are generally undisturbed and in relatively healthy condition, the more bullet shaped tip of the embodiment shown in FIG. 3 is sufficient to facilitate advancement of the lead 36. However, sometimes the epicardium 28 and/or pericardium 33 have been damaged, either by disease or previous trauma, resulting in the presence of tough adhesions or scar tissue. The more pointed cone shaped tip 54 of the embodiment shown in FIG. 2 may be required to effectively traverse such adhesions or scar tissue. Prior to inserting the lead 36, the surgeon may evaluate the implant site and select an appropriate tip 54, i.e. pointed or blunt, as deemed necessary to pierce the epicardium 28 and or pericardium 33 and dilate the tract through the heart 12 to facilitate insertion of the lead 36.

According to one embodiment, as shown in FIGS. 2 and 3, the tapered tip 54 is configured to securely couple with the blunt distal tip 42 of the lead 36. According to one embodiment, the diameter a of the proximal end 54 a of the tip 54 is sized to receive the distal tip 42 of the lead 36. According to other embodiments, the tip 54 and distal tip 42 of the lead 36 are provided with complementary threads for rotational coupling, or are provided with a complementary interlock or other structure for coupling.

FIG. 4 shows another embodiment, in which the tapered tip 54 is positioned adjacent to the distal tip 42 of the pacing lead 36 without securely coupling to the lead 36. The tapered tip 54 rides along the tether 45 in front of the lead 36 to facilitate the lead 36 in passing through the myocardium 32. A tip 54 according to the present embodiment may be used in conjunction with any such commercially available myocardial lead. According to another embodiment, the tapered tip 54 is integrally formed at the distal end 42 of the lead 36.

FIG. 5 shows another embodiment in which the system is further provided with a lock 60 and lock housing 61 as is described in the above-identified application “Distal or Proximal Fixation of Over-the-Tether Myocardial Leads”. The tip bore 56 has a diameter c greater than the diameter of the tether 45 such that the tip 54 easily passes over the tether 45, but smaller than a diameter of the lock 60 formed on the tether 45. The tip 54 and lead 36 are easily threaded over the tether 45 and advanced along the tether 45. When the tip 54 contacts the lock 60, the tip 54 and lead 36 are prevented from advancing further along the tether 45. The tapered tip 54 is used to prevent the lead 36 from advancing over the lock 60, and to provide spacing between the lead 36 and the anchor mechanism 44.

According to another embodiment, the tip 54 is made from a water-soluble material, such that the tip 54 will dissolve upon placement within the myocardium 32. The tip 54 may be made from any biocompatible, water-soluble material known in the art, such as a sugar. In one embodiment, the tip 54 is made from mannitol. In another embodiment, the tip 54 is made from polyethylene glycol (“PEG”). The molecular weight of the PEG can be selected to achieve a desired dissolution time of the tapered tip 54. In yet another embodiment, additives known in the art are used to further control the dissolution time. According to another embodiment, the tip 54 is made of an ablatable material.

A dissolvable tip 54 reduces the amount of foreign matter located in the heart 12 following dissolution. This may reduce irritation in the heart 12, as well as the formation of scar tissue. Addition of the tip 54 does not increase the overall size of the lead 36 chronically implanted in the heart 12. Following dissolution of the tip 54, the lead 36 may be advanced over the lock 60 to mate the lock 60 with the lock housing 61. In addition, the dissolved portion of the dissolving tip 54 provides a lubricating coating or film within the tract to further facilitate passage of the lead 36.

FIGS. 6A and 6B show another embodiment of the lead 36, in which a fixation mechanism 62 is provided at the distal tip 42 of the lead 36. Such a fixation mechanism 62 facilitates fixation of the lead 36 to myocardial tissue 32. The above-identified application “Myocardial Lead with Fixation Mechanism” describes various fixation mechanisms suitable for use with a lead 36 according to the present embodiment. The tapered tip 54 is dissolvable as previously described and is configured to mate with the fixation mechanism 62. According to one embodiment, the fixation mechanism 62 is received in the tip bore 56.

Throughout insertion of the lead 36 into the heart 12, the tapered tip 54 facilitates passage of the lead 36 through the tract and masks the fixation mechanism 62, which may include sharp edges or points. Upon dissolution of the tip 54, the fixation mechanism 62 is revealed and operable to retain the lead 36 in a stable position. According to one embodiment, the fixation mechanism 62 is retained in the tip bore 56 in a first collapsed or retracted configuration, as is shown in FIG. 6A. Following dissolution of the tip 54, the fixation mechanism 62 deploys to a second expanded configuration, as is shown in FIG. 6B.

According to another embodiment, the tip 54 contains a pharmaceutical additive to treat implant trauma. Such an additive may be provided to reduce myocardial irritation or inflammation. This pharmaceutical additive may administer a “bolus” therapeutic agent to treat the implant trauma. In one embodiment, the tip 54 is made of a dissolvable material as described above but which also includes a steroid (or other therapeutic drug) released as the tip 54 dissolves. According to another embodiment, the tip 54 is formed of a material provided with a coating that is drug eluting. The tip 54 may be chosen to have an appropriate amount of steroid (or other therapeutic drug) for a particular situation.

In one embodiment, pharmaceutical additives as previously described are provided on other portions of the lead 36 in addition to or instead of the tip 54. In one embodiment, the drug eluting feature is provided as one or more discrete steroid/polymeric rings or collars 64 positioned on the lead 36 to contact the myocardium 32 upon implantation and anchoring (See FIG. 2). In another embodiment, the implanted portion of the lead 20 is coated with a drug (e.g., steroid) eluting coating, such as a paint stripe (not shown). In another embodiment, shown in FIG. 7, a polymeric lead body tubing 66 may be fashioned from a steroid-loaded polymer composite. In each of these embodiments, a therapeutic amount of steroid is included on the implanted portion of the lead 36.

Various controlled-release techniques known in the art may be incorporated into these embodiments to deliver the therapeutic drug in the right amount and with the right time distribution.

Various modifications and additions can be made to the exemplary embodiments discussed without departing from the scope of the present invention. Accordingly, the scope of the present invention is intended to embrace all such alternative, modifications, and variations as fall within the scope of the claims, together with all equivalents thereof. 

1. A lead for use in connection with a myocardial lead attachment system of the type having an anchor for engaging the heart and a tether extending from the anchor, the lead including: a lead body having a proximal end, a distal end and a lumen for accepting the tether; and a tapered tip separate from the lead and positioned adjacent the distal end of the lead body, wherein the tip has a longitudinal through-hole for accepting the tether.
 2. The lead of claim 1 wherein the tip is coupled to the distal end of the lead body.
 3. The lead of claim 1 wherein the tip is free from fixed connection to the lead.
 4. The lead of claim 1 wherein the tip has a reduced diameter in a direction from a proximal end to a distal end to reduce trauma to the heart as the lead is advanced through the myocardium.
 5. The lead of claim 4 wherein the tip is cone shaped.
 6. The lead of claim 4 wherein the tip is bullet shaped.
 7. The lead of claim 1 wherein the tip is made from a dissolvable material.
 8. The lead of claim 7 wherein the tip is formed from a water-soluble material.
 9. The lead of claim 7 wherein the tip is formed from one of sugar, mannitol or polyethylene glycol.
 10. The lead of claim 7 wherein a period of time necessary to dissolve the tip is less than a period of time in which scar tissue forms about the tip.
 11. The lead of claim 7 further comprising a fixation mechanism coupled to the distal end of the lead, wherein the tip has an opening to receive the fixation mechanism and retain the fixation mechanism in a retracted configuration and upon dissolution of the tip the fixation mechanism deploys to an expanded configuration.
 12. The lead of claim 7 wherein the tip includes a therapeutic drug for release as the tip dissolves.
 13. The lead of claim 12 wherein the therapeutic drug is a steroid.
 14. The lead of claim 1 wherein the tip is formed from a therapeutic drug-eluting material.
 15. The lead of claim 14 wherein the drug is a steroid.
 16. The lead of claim 1, further comprising a therapeutic drug attached to an outer surface of a portion of the lead body.
 17. The lead of claim 16 wherein the therapeutic drug is a steroid.
 18. The lead of claim 16 wherein the drug is attached onto an implanted portion of the lead.
 19. The lead of claim 1 wherein the tip is formed from an ablatable material.
 20. The lead of claim 1 further comprising: a lock housing on the lead; and a lock formed on a distal end of the tether and lock having a first diameter, wherein the tip through-hole has an internal diameter smaller than the lock first diameter.
 21. A method of implanting a myocardial lead, the method comprising: advancing an anchor mechanism coupled to a distal end of a tether through the myocardium to an implant site; selecting an appropriate dilating tip having an internal through-hole; threading the tip and lead onto the tether such that the tip is distal to the lead; and advancing the tip and lead over the tether to the implant site.
 22. The method of claim 21 further comprising coupling the tip to a distal end of the lead.
 23. The method of claim 21 further comprising allowing the tip to dissolve.
 24. The method of claim 23 wherein threading the tip and lead onto the tether further comprises inserting a fixation mechanism coupled to a distal end of the lead into an opening in the tip in a retracted configuration and dissolving the tip further includes allowing the fixation mechanism to deploy to an expanded configuration.
 25. The method of claim 23 further comprising releasing a therapeutic drug from the tip as the tip dissolves.
 26. A method of implanting a lead into a myocardium of a heart, the method comprising: attaching a proximal end of an anchor mechanism and tether arrangement to a needle; advancing the needle through the heart at least until the proximal end of the tether 45 exits the heart; detaching the needle from the tether; tensioning the proximal end of the tether to cause the anchor mechanism to engage the heart; and advancing a lead over the tether into the heart. 